This invention relates to a Two-Way Automated Communications System (TWACS) used by electrical utilities to communicate between the utility and a customer site; and, more particularly, to concurrent outbound communications in a TWACS communications system.
In an electrical utility, a TWACS concurrent outbound signal injection scheme is employed to simultaneously route outbound communications on three phases of the voltage waveform propagating through the utility's low voltage distribution network. In this regard, a TWACS outbound signal is the “common language” used to describe a signal generated by Substation Control Equipment (SCE) utilized in the TWACS power-line communication system. The outbound signal is carried on an AC distribution voltage routed to remote locations (e.g., customer sites) and received by Remote Communication Equipment (RCE) installed at the remote location. Commands contained in an outbound signal cause the RCE to perform various tasks, one of which is transmitting a communication or signal back to the SCE. This response is referred to as an inbound signal or inbound communication.
SCE equipment installed at a power distribution substation uses expensive coupling transformers to inject an outbound signal into a waveform propagated through the utility's power distribution system, and to acquire and detect an inbound signal on the system's high voltage circuits. These circuits are typically 7 kV-35 kV circuits. Both the SCE and RCE have to transmit at relatively high current levels to produce a signal that can be detected at the other end of the power distribution system. In the system, there are usually a large number of RCE points per distribution substation. A distribution substation then typically feeds a large number of distribution transformers that step down the high voltage propagated through the power distribution system to low voltage levels necessary for customer use. And, while there are typically few RCE points per distribution transformer, this topology, which is common in the United States, suits the current TWACS implementation well.
However, in certain foreign countries and some domestic applications, the topology of a power distribution system is significantly different from the topology described above. In these applications, a power distribution system or network has many fewer distribution transformers and many more electrical utility customers per distribution transformer. In addition, the accessibility to install TWACS SCE equipment in the power distribution substations in some of these utilities can be severely limited.